Do you when oxygen was discovered?

1. Oxygen was first discovered by Swedish pharmacist Carl Wilhelm Scheele in 1772 or 1773. He produced the gas by heating mercuric oxide with various nitrates.
2. However, his publication on the discovery was not published until 1777. In 1774, British clergyman Joseph Priestley focused sunlight on mercuric oxide and discovered a gas was formed- oxygen.
3. As he published his finding in 1775, he is often mistaken as the true discoverer of oxygen. This is not the case. Scheele was the first person to discover oxygen.
4. There are three stable isotopes of oxygen. Oxygen-16 is the most abundant (over 99% of oxygen in the air is oxygen-16).
5. Liquid and solid oxygen have a light sky-blue color.
6. Oxygen is the third most abundant element in the universe (after hydrogen and helium). It is the most abundant in the Earth’s crust.
7. Proteins, carbohydrates and fats (all essential for animals and humans) contain oxygen.
8. One form of oxygen, ozone, protects the Earth from ultraviolet radiation which is harmful to humans (can cause cancers).